Electro optical devices with reduced filter thinning on the edge pixel photosites and method of producing same

ABSTRACT

The present invention relates to semiconductor devices with a reduced filter thinning of outer photosites and a method for reducing the thinning of filter layers of the outer photosites. A semiconductor device includes a main surface including a plurality of photosites and bonding pads defined in the main surface, wherein the photosites include inner photosites and outer photosites. The semiconductor device further includes a clear layer deposited over the main surface exclusive of the bonding pads and outer photosites, and a first primary color filter layer deposited over at least first inner photosite and first outer photosite, the first primary color filter transmitting a primary color.

THIS APPLICATION IS A DIVISIONAL OF APPLICATION SER. NO. 09/196,394,FILED NOV. 19, 1998

Attention is directed to copending application U.S. patent applicationSer. No. 09/641292, filed Aug. 18, 2000, entitled, “ELECTRO OPTICALDEVICES WITH REDUCED FILTER THINNING ON THE EDGE PIXEL PHOTOSITES ANDMEHTOD FOR PRODUCING SAME”. The disclosure of this application is herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to electro optical devices with a reducedfilter thinning on the edge or outer pixels and a method for reducingthe thinning of filter layers on the pixel photosites dosest to the edgeof an electro optical device such as a photosensitive chip, as would beused, for example, in a full-color digital copier or scanner.

BACKGROUND OF THE INVENTION

Image sensors for scanning document images, such as charge coupleddevices (CCDs), typically have a row or linear array of photositestogether with suitable supporting circuitry integrated onto asemiconductor chip. Usually, a sensor is used to scan line by lineacross the width of a document with the document being moved or steppedlengthwise in synchronism therewith. A typical architecture for such asensor array is given, for example, in U.S. Pat. No. 5,153,421.

In a full-pagewidth image scanner, there is provided a linear array ofphotosensors which extends the full width of an original document, suchas eleven inches. When the original document moves past the lineararray, each of the photosensors converts reflected light from theoriginal image into electrical signals. The motion of the original imageperpendicular to the linear array causes a sequence of signals to beoutput from each photosensor, which can be converted into digital data.

A currently preferred design for creating such a long linear array ofphotosensors is to provide a set of relatively small semiconductorchips, each semiconductor chip defining thereon a linear array ofphotosensors along with ancillary circuit devices. These chips areassembled end-to-end to form a single linear array of photosensors asdisclosed in U.S. Pat. No. 5,473,513. However, there are also singlechip applications in which a single chip having a linear array may beused for sensing images and converting those images into electricalsignals to be output from each photosensor. These electrical signals canbe converted into digital data.

With the gradual introduction of color-capable products into the officeequipment market, it has become desirable to provide scanning systemswhich are capable of converting light from full-color images intoseparate trains of image signals, each train representing one primarycolor. In order to obtain the separate signals relating to colorseparations in a full-color image, one technique is to provide on asemiconductor chip multiple parallel linear arrays of photosensors, eachof the parallel arrays being sensitive to one primary color. Typically,this arrangement can be achieved by providing multiple linear arrays ofphotosensors which are physically identical except for a translucentprimary-color overlay over the photosensitive areas, or “photosites,”for that linear array. In other words, the linear array which issupposed to be sensitive to red light only will have a translucent redlayer placed on the photosites thereof, and such would be the case for ablue-sensitive array and a green-sensitive array. As the chip is exposedto an original full-color image, only those portions of the image, whichcorrespond to particular primary colors, will reach those photosensorsassigned to the primary color. These chips can also be assembled end toend to form a full width array comprising a multiple parallel lineararrays of photosites.

The most common substances for providing these translucent filter layersover the photosites is polyimide or acrylic. For example, polyimide istypically applied in liquid form to a batch of photosensor chips whilethe chips are still in undiced, wafer form. After the polyimide liquidis applied to the wafer, the wafer is centrifuged to provide an evenlayer of a particular polyimide. In order to obtain the polyimide havingthe desired primary-color-filtering properties, it is well known to dopethe polyimide with either a pigment or dye of the desired color, andthese dopants are readily commercially available. When it is desired toplace different kinds of color filters on a single chip, a typicaltechnique is to first apply an even layer of polyimide over the entiremain surface of the chip (while the chip is still part of the wafer) andthen remove the unnecessary parts of the filter by photo-etching oranother well known technique. Typically, the entire filter layer placedover the chip is removed except for those areas over the desired set ofphotosites. Acrylic is applied to the wafer in a similar manner.

SUMMARY OF THE INVENTION

According to a first embodiment of the present invention, asemiconductor device includes a main surface including a plurality ofphotosites and bonding pads defined in the main surface, wherein thephotosites include inner photosites and outer photosites. A dear layeris deposited over the main surface exclusive of the bonding pads andouter photosites. A first primary color filter layer is deposited overat least first inner photosite and first outer photosite, the firstprimary color filter transmitting a first primary color. A secondprimary color filter layer is deposited over at least a second innerphotosite and a second outer photosite, wherein the second primary colorfilter layer transmits a second primary color. A third primary colorfilter layer is deposited over at least a third inner photosite and athird outer photosite, wherein the third primary color layer transmits athird primary color. The clear layer and filter layers are preferablypolyimide or acrylic.

According to a second embodiment, a semiconductor chip includes a mainsurface including a plurality of photosites and bonding pads defined inthe main surface, wherein the photosites include inner photosites andouter photosites. A first clear layer is deposited over the main surfaceexclusive of the bonding pads, and a second clear layer is depositedover the main surface exclusive of the bonding pads and outerphotosites. A first primary color filter layer is deposited over atleast first inner photosite and first outer photosite. The first primarycolor filter transmits a primary color. A second primary color filterlayer is deposited over at least a second inner photosite and a secondouter photosite, wherein the second primary color filter layer transmitsa second primary color. A third primary color filter layer is depositedover at least a third inner photosite and a third outer photosite,wherein the third primary color layer transmits a third primary color.The clear layer, the second clear layer and the filter layers arepreferably polyimide or acrylic

The semiconductor devices of the first embodiment may be placed in adigital copier, which includes a raster input scanner scanning documentsto generate digital image signals, the raster input scanner including aplurality of generally rectangular chips, which are assembled end to endon a substrate forming a full width array of multiple parallel lineararrays of photosites. Each chip includes a main surface includingbonding pads and the photosites defined in the main surface, wherein thephotosites include inner photosites and outer photosites, a clear layerdeposited over the main surface exclusive of the bonding pads and outerphotosites, and a first primary color filter layer deposited over atleast first inner photosite and first outer photosite, the first primarycolor filter transmitting a primary color.

The semiconductor devices of the second embodiment may be placed in adigital copier including a raster input scanner scanning documents togenerate digital image signals, the raster input scanner including aplurality of generally rectangular chips, which are assembled end to endon a substrate forming a full width array of multiple parallel lineararrays of photosites. Each chip includes a main surface includingbonding pads and the photosites defined in the main surface, wherein thephotosites include inner photosites and outer photosites, a clear layerdeposited over the main surface exclusive of the bonding pads, a secondclear layer deposited over the main surface exclusive of the bondingpads and outer photosites, and a first primary color filter layerdeposited over at least first inner photosite and first outer photosite,the first primary color filter transmitting a primary color.

A method for fabricating a photosensitive device of the first embodimentcomprises providing a semiconductor wafer having a main surface definingchip areas separated by V-grooves, the chip areas defining bonding padsand three rows of photosites, wherein the photosites include innerphotosites, outer photosites and bonding pads; depositing a dear layeron the semiconductor wafer, soft baking the semiconductor wafer;exposing selective areas of the semiconductor wafer, etching the clearlayer covering the bonding pads and outer photosites from thesemiconductor wafer; hard baking the semiconductor wafer; and depositinga first primary color filter layer over at least first inner photositeand first outer photosite, the first primary color filter transmitting aprimary color. The method for fabricating a semiconductor deviceincludes dicing the semiconductor wafer to provide semiconductor chips.

A method for fabricating a photosensitive chip of the second embodimentcomprises providing a semiconductor wafer having a main surface definingchip areas separated by V-grooves, the chip areas defining bonding padsand three rows of photosites, wherein the photosites include innerphotosites, outer photosites and bonding pads; depositing a first clearlayer on the semiconductor wafer; soft baking the semiconductor wafer;exposing selective areas of the semiconductor wafer, etching the firstclear layer covering the bonding pads from the semiconductor wafer; hardbaking the semiconductor wafer; depositing a second clear layer on thesemiconductor wafer; exposing selective areas of the semiconductorwafer; etching the second clear layer covering the bonding pads andouter photosites from the semiconductor wafer; hard baking thesemiconductor wafer; and depositing a first primary color filter layerover at least first inner photosite and first outer photosite, the firstprimary color filter transmitting a primary color. The method forfabricating a semiconductor device further includes dicing thesemiconductor wafer to provide semiconductor chips.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing two chips relevant to the presentinvention;

FIG. 2 is a perspective view showing a semiconductor wafer relevant tothe present invention;

FIG. 3 is a cross sectional view along the line 3—3 in the direction ofthe arrows in FIG. 1, showing polyimide or acrylic layers deposited on asection of the semiconductor wafer in accordance with the prior art;

FIG. 4 is a partial cross sectional view along the line 4—4 in thedirection of the arrows in FIG. 1, showing polyimide or acrylic layersdeposited on a section of the semiconductor wafer in accordance with theprior art;

FIG. 5 is a partial cross-sectional view along the line 4—4 in thedirection of the arrows in FIG. 1, showing a section of thesemiconductor wafer before the acrylic or polyimide layers are depositedin accordance with embodiments of the present invention;

FIG. 6 shows a clear layer deposited on the section of the semiconductorwafer of FIG. 5 in accordance with the embodiments of the presentinvention;

FIG. 7 shows outer photosites etched out of the section of thesemiconductor wafer shown in FIG. 6 in accordance with a firstembodiment of the present invention;

FIG. 8 shows a filter layer deposited on the semiconductor wafer of FIG.7 in accordance with the first embodiment of the present invention;

FIG. 9 shows a second dear layer deposited on the dear layer of FIG. 6in accordance with a second embodiment of the present invention;

FIG. 10 shows the second clear layer of the outer photosites etched outof the section of the semiconductor wafer shown in FIG. 9 in accordancewith the second embodiment of the present invention;

FIG. 11 shows a filter layer deposited on the semiconductor wafer ofFIG. 10 in accordance with the second embodiment of the presentinvention; and

FIG. 12 is a partial schematic elevational view of an example of adigital copier, which can employ the photosensitive chips produced fromthe first and second embodiments of the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

FIG. 1 is a perspective view showing two photosensitive chips 10relevant to the claimed invention. The chips 10 are generally made of asemiconductor substrate, as is known in the art, in which circuitry andother elements are formed, such as by photolithographic etching. A fewof the most relevant structures are a linear array of pixel photosites12, each of which forms the photosensitive surface of photosensorcircuitry within each chip 10, and a set of bonding pads 14. The pixelphotosites 12 are typically arranged in a linear array along one maindimension of each chip 10, with each pixel photosite 12 along the arraycorresponding to one pixel in the image signal. As will be described indetail below, the pixel photosite 12 includes photosites 12B, 12G and12R for sensing the three primary colors (blue, green and red)corresponding to the pixel.

The bonding pads 14 are distinct surfaces on the main surface of thechips 10, and are intended to accept wire bonds attached thereto. Thebonding pads 14 thus serve as the electronic interface between the chips10 and any external circuitry. The circuitry for obtaining signalsrelated to light directed to the pixel photosites 12, and for unloadingimage data from the chips 10 is generally indicated as 16. The circuitry16 is generally deposited between the linear array of pixel photosites12 and a linear array of bonding pads 14.

Chips 10 are typically formed in batches on semiconductor wafers, whichare subsequently cleaved, or “diced,” to create individual chips.Typically, the semiconductor wafers are made of silicon. As is known inthe art, photolithographically etched V-grooves 18 define precisely theintended boundaries of a particular chip 10 for dicing. Thus, all of thepixel photosites 12, bonding pads 14 and circuitry 16 for relativelylarge number of chips 10 are etched simultaneously onto a singlesemiconductor wafer 20 as shown in FIG. 2. The region between theV-grooves 18 is called the tab region. The pixel photosite 12 adjacentto each V-groove is referred to as an outer pixel photosite 12 _(o).Each outer pixel photosite 12 _(o) consists of three outer photosites12B, 12G, and 12R. The other pixel photosites 12 are referred to asinner pixel photosites 12 _(I) and each inner pixel photosite 12 _(I)consists of three inner photosites 12B, 12G, and 12R. The innerphotosites 12B and outer photosites 128 form a first row of photosites.The inner photosites 12G and the outer photosites 12G form a second rowof photosites. The inner photosites 12R and the outer photosites 12Rform a third row of photosites.

FIG. 2 shows a typical semiconductor wafer 20, in isolation, wherein arelatively large number of chips 10 are created in the wafer 20 prior todicing thereof. Each chip 10 has a distinct chip area within the mainsurface of the wafer 20. The phrase “chip area” refers to a defined areawithin the main surface of the wafer 20 which is intended to comprise adiscrete chip 10 after the dicing step, when individual chips 10 areseparated from the rest of the wafer 20.

FIG. 3 is a cross sectional view along line 3—3 in the direction of thearrows in FIG. 1. On the main surface of chip 10 there is provided aninner pixel photosite 12, with three separate inner photosites 12B, 12Gand 12R, each sensitive to one primary color. As shown in FIG. 3, withineach inner pixel photosite 12 _(I) is deposited a photosite 12G,sensitive to green light, a photosite 12R sensitive to red light, and aphotosite 12B, sensitive to blue light. The three photosites 12B, 12Gand 12R are on the whole identical as circuit elements except that thesurface of each photosite 12B, 12G and 12R is superimposed thereon by adistinct primary-color filter layer 30. The blue filter layer, greenfilter layer and red filter layer are indicated by reference numerals30B, 30G, and 30R.

As is known in the art, such filter layers preferably comprise apolyimide or acrylic which has been doped with a commercially availabledye or pigment blended to yield a primary color filter. As is furtherknown in the art, it is common to provide filter layers such as 30B, 30Gand 30R, by first placing a polyimide or acrylic in liquid form over theentire main surface of the chip 10, and then removing the polyimide oracrylic by photolithography in all areas of the chip 10 except where thefilter area is desired. To ensure a uniform coating of these materials,the semiconductor wafer 20 is partially planarized by using clear layer40, which is preferably a dear polyimide or clear acrylic layer. Thisclear layer 40 acts to smooth the topography of the semiconductor wafer20 and partially fill the V-grooves 18 as shown in FIG. 4. Since theclear layer 40 only partially planarizes the semiconductor wafer 20, theV-grooves 18 still allow some of the filter material to be channeledaway from the outer pixel photosite 12 _(o), causing thinning of thefilter material over the outer pixel photosite 12 _(o) as shown in FIG.4. The outer pixel photosites 12 _(o) on the semiconductor wafer 20 havesubstantially thinner filter layers 30 than the inner pixel photosites12 _(I) due to the topography of the semiconductor wafer 20 as explainedabove. The two embodiments of the present invention enhance the imagesensing capability of the photosensitive chips 10 by increasing thethickness of the filter layers 30 of the outer pixel photosites 12 _(o).

FIG. 5 is a cross-sectional view along the line 4—4 in the direction ofthe arrows in FIG. 1, showing a section of the semiconductor wafer 20before the acrylic or polyimide layers are deposited in accordance withthe first embodiment of the present invention. A clear layer 40, whichis preferably polyimide or acrylic, is deposited on the semiconductorwafer 20 to smooth the topography of the semiconductor wafer 20 as inthe prior art. The coated semiconductor wafer 20 is soft baked(partially baked), and certain areas of the semiconductor wafer 20 areselected for exposure to ultraviolet light using a mask. The dear layer40 is etched out of the bonding pads 14. An etched out bonding pad 14 isshown in prior art FIG. 3. According to the first embodiment of thepresent invention, the dear layer 40 is also etched out of the outerpixel photosites 12 _(o) as shown in FIG. 7. Preferably, the clear layer40 is etched out using a well-known solvent. The semiconductor wafer 20is then hard baked. A filter layer 30 is deposited on the semiconductorwafer 20 as shown in FIG. 8. By etching out the outer pixel photosites12 _(o), the outer pixel photosites 12 _(o) now have a deeper well tocollect additional filter material so that there is a thicker filterlayer 30 in the outer pixel photosites 12 _(o) as indicated in FIG. 8.This enhances the image sensing capability of the photosensitive chips10.

If only one filter layer 30 was to be deposited on semiconductor wafer20, then the semiconductor wafer 20 would be soft baked. Then, certainareas of the semiconductor wafer 20 would be selectively exposed toultraviolet light using a mask and the filter layer 30 would be etchedout of the semiconductor wafer 20 except for the pixel photosites 12.The semiconductor wafer 20 would then be hard baked and diced to providechips 10.

However, two additional filter layers 30 are preferably added tosemiconductor wafer 20. Therefore, after the first filter layer 30 isdeposited on the semiconductor wafer 20, the semiconductor wafer 20 issoft baked. Certain areas of the semiconductor wafer 20 are selected forexposure to ultraviolet light using a mask. Preferably, the filter layer30 is etched out of the semiconductor wafer 20 except for one row ofphotosites in each chip area, which is shown by the partial crosssection of chips 10 in FIG. 8. The two other rows of photosites in eachchip area have substantially the same configuration as shown in thepartial cross section of chips 10 in FIG. 7. A second filter layer 30 isdeposited on the semiconductor wafer 20, and these two rows now havesubstantially the same configuration as shown in FIG. 8. Thesemiconductor wafer 20 is then soft baked, selectively exposed toultraviolet light, selectively etched and hard baked so that two rows ofphotosites in each chip area each have a different filter layer 30. Thetwo rows having filter layers 30 in each chip area have substantiallythe same configuration as shown by the partial cross section in FIG. 8.The last row of photosites, which does not have a filter layer 30, hassubstantially the same configuration as shown in the partial crosssection in FIG. 7.

A third filter layer 30 is deposited on the semiconductor wafer 20. Thesemiconductor wafer 20 is then soft baked, selectively exposed toultraviolet light, selectively etched and hard baked so that three rowsof photosites now have substantially the same configuration as shown inFIG. 8. However, each filter layer 30 preferably has a different filtermaterial. Preferably, the three filter layers 30 are red, green andblue.

In the second embodiment of the present invention, there is provided asemiconductor wafer 20 having a first dear layer 40 as in the prior art.The coated semiconductor wafer 40 is soft baked (partially bake) andexposed to ultraviolet light as in the prior art The first clear layer40 is etched out of the bonding pads 14. An etched out bonding pad 14 isshown in prior art FIG. 3. The semiconductor wafer 20 is then hardbaked. A second dear layer 50 is deposited on the semiconductor wafer 20as shown in FIG. 9. The twice coated semiconductor wafer 20 is softbaked (partially baked), and exposed to ultraviolet light. The secondclear layer 50 is etched out of both the outer pixel photosites 12 _(o)as shown in FIG. 10 and the bonding pads 14 as shown in prior art FIG.3. Preferably, the second clear layer 50 is etched out using awell-known solvent. The semiconductor wafer 20 is then hard baked. Afilter layer 30 is deposited on the semiconductor wafer 20 as shown inFIG. 11. By etching out the outer pixel photosites 12 _(o), the outerpixel photosites 12 _(o) now have a deeper well than the inner pixelphotosites 12 _(I) to collect additional filter material so that thereis a thicker filter layer 30 in the outer pixel photosites 12 _(o) asindicated in FIG. 11. This enhances the image sensing capability of thephotosensitive chips 10.

If only one filter layer 30 was to be deposited on semiconductor wafer20, then the semiconductor wafer 20 would be soft baked. Then, certainareas of the semiconductor wafer 20 would be selectively exposed toultraviolet light using a mask and the filter layer 30 would be etchedout of the semiconductor wafer 20 except for the pixel photosites 12.The semiconductor wafer 20 would then be hard baked and diced to providechips 10.

However, two additional filter layers 30 are preferably added tosemiconductor wafer 20. Therefore, after the first filter layer 30 isdeposited on the semiconductor wafer 20, the semiconductor wafer 20 issoft baked. Certain areas of the semiconductor wafer 20 are selected forexposure to ultraviolet light using a mask Preferably, the filter layer30 is etched out of the semiconductor wafer 20 except for one row ofphotosites in each chip area, which is shown by the partial crosssection of chips 10 in FIG. 11. The two other rows of photosites in eachchip area have substantially the same configuration as in the partialcross section of chips 10 in FIG. 10. A second filter layer 30 isdeposited on the semiconductor wafer 20, and these two rows now havesubstantially the same configuration as shown in FIG. 11. Thesemiconductor wafer 20 is then soft baked, selectively exposed toultraviolet light, selectively etched and hard baked so that two rows ofphotosites in each chip area each have a different filter layer 30. Thetwo rows having filter layers 30 in each chip area have substantiallythe same configuration as shown by the partial cross section in FIG. 11.The last row of photosites, which does not have a filter layer 30, hassubstantially the same configuration as shown by the partial crosssection in FIG. 10.

A third filter layer 30 is deposited on the semiconductor wafer 20. Thesemiconductor wafer 20 is then soft baked, selectively exposed toultraviolet light, selectively etched and hard baked so that three rowsof photosites now have substantially the same configuration as shown inFIG. 11. However, each filter layer 30 preferably has a different filtermaterial. Preferably, the three filter layers 30 are red, green andblue.

FIG. 12 is a partial schematic elevational view of a digital copier,which can utilize the photosensitive chips 10 of the present inventionby assembling them in generally the same manner as in U.S. Pat. No.5,153,421. However, it is understood that the photosensitive chips 10may be used together in a full width array or independently in a singlechip application in any imaging or scanning device.

An original document is positioned in a document handler 227 on araster-input scanner (RIS) indicated generally by reference numeral 228.The RIS contains document illumination lamps, optics, a mechanicalscanning device and a plurality of photosensitive chips 10 as shown inFIG. 1. The photosensitive chips 10 may include any one of thephotosensitive arrays described above. The RIS captures the entireoriginal document and converts it to a series of raster scan lines. Thisinformation is transmitted to an electronic subsystem (ESS) whichcontrols a raster output scanner (ROS).

The digital copier employs a photoconductive belt 210. Preferably, thephotoconductive belt 210 is made from a photoconductive material coatedon a ground layer, which, in tum, is coated on an anti-curl backinglayer. Belt 210 moves in the direction of arrow 213 to advancesuccessive portions sequentially through the various processing stationsdeposited about the path of movement thereof. Belt 210 is entrainedabout stripping roller 214, tensioning roller 220 and drive roller 216.As roller 216 rotates, it advances belt 210 in the direction of arrow213.

Initially, a portion of the photoconductive surface passes throughcharging station A At charging station A, a corona generating deviceindicated generally by the reference numeral 222 charges thephotoconductive belt 210 to a relatively high, substantially uniformpotential.

At an exposure station B, a controller or electronic subsystem (ESS),indicated generally by reference numeral 229, receives the image signalsrepresenting the desired output image and processes these signals toconvert them to a continuous tone or grayscale rendition of the imagewhich is transmitted to a modulated output generator, for example theraster output scanner (ROS), indicated generally by reference numeral230. Preferably, ESS 229 is a self-contained, dedicated minicomputer.The image signals transmitted to ESS 229 may originate from a RIS 228 asdescribed above or another type of scanner utilizing the photosensitivechips 10, thereby enabling the digital copier to serve as a remotelylocated printer for one or more scanners. Alternatively, the printer mayserve as a dedicated printer for a high-speed computer or for one ormore personal computers. The signals from ESS 229, corresponding to thecontinuous tone image desired to be reproduced by the printer, aretransmitted to ROS 230. ROS 230 includes a laser with rotating polygonmirror blocks. The ROS 230 will expose the photoconductive belt 210 torecord an electrostatic latent image thereon corresponding to thecontinuous tone image received from ESS 229. As an alternative, ROS 230may employ a photosensitive array of light emitting diodes (LEDs)arranged to illuminate the charged portion of photoconductive belt 210on a raster-by-raster basis.

After the electrostatic latent image has been recorded onphotoconductive surface 212, belt 210 advances the latent image to adevelopment station, C, where toner, in the form of liquid or dryparticles, is electrostatically attracted to the latent image usingcommonly known techniques. The latent image attracts toner particlesfrom the carrier granules forming a toner powder image thereon. Assuccessive electrostatic latent images are developed, toner particlesare depleted from the developer material. A toner particle dispenser,indicated generally by the reference numeral 244, dispenses tonerparticles into developer housing 246 of developer unit 238.

With continued reference to FIG. 12, after the electrostatic latentimage is developed, the toner powder image present on belt 210 advancesto transfer station D. A print sheet 248 is advanced to the transferstation, D, by a sheet feeding apparatus, 250. Preferably, sheet feedingapparatus 250 includes a nudger roll 251 which feeds the uppermost sheetof stack 254 to nip 255 formed by feed roll 252 and retard roll 253.Feed roll 252 rotates to advance the sheet from stack 254 into verticaltransport 256. Vertical transport 256 directs the advancing sheet 248 ofsupport material into the registration transport 290 and past imagetransfer station D to receive an image from photoreceptor belt 210 in atimed sequence so that the toner powder image formed thereon contactsthe advancing sheet 248 at transfer station D. Transfer station Dincludes a corona-generating device 258, which sprays ions onto thebackside of sheet 248. This attracts the toner powder image fromphotoconductive surface 212 to sheet 248. The sheet is then detachedfrom the photoreceptor by corona generating device 259 which spraysoppositely charged ions onto the back side of sheet 248 to assist inremoving the sheet from the photoreceptor. After transfer, sheet 248continues to move in the direction of arrow 260 by way of belt transport262, which advances sheet 248 to fusing station F.

Fusing station F includes a fuser assembly indicated generally by thereference numeral 270 which permanently affixes the transferred tonerpowder image to the copy sheet Preferably, fuser assembly 270 includes aheated fuser roller 272 and a pressure roller 274 with the powder imageon the copy sheet contacting fuser roller 272. The pressure roller 274is loaded against the fuser roller 272 to provide the necessary pressureto fix the toner powder image to the copy sheet. The fuser roller 272 isinternally heated by a quartz lamp (not shown). Release agent stored ina reservoir (not shown), is pumped to a metering roll (not shown). Atrim blade (not shown) trims off the excess release agent. The releaseagent transfers to a donor roll (not shown) and then to the fuser roll272. Or alternatively, release agent is stored in a presoaked web (notshown) and applied to the fuser roll 272 by pressing the web againstfuser roll 272 and advancing the web at a slow speed.

The sheet then passes through fuser 270 where the image is permanentlyfixed or fused to the sheet. After passing through fuser 270, a gate 280either allows the sheet to move directly via output 284 to a is finisheror stacker, or deflects the sheet into the duplex path 300,specifically, first into single sheet inverter 282 here. That is, if thesheet is either a simplex sheet, or a completed duplex sheet having bothside one and side two images formed thereon, the sheet will be conveyedvia gate 280 directly to output 284. However, if the sheet is beingduplexed and is then only printed with a side one image, the gate 280will be positioned to deflect that sheet into the inverter 282 and intothe duplex loop path 300, where that sheet will be inverted and then fedto acceleration nip 202 and belt transports 310, for recirculation backthrough transfer station D and fuser 270 for receiving and permanentlyfixing the side two image to the backside of that duplex sheet, beforeit exits via exit path 284.

After the print sheet is separated from photoconductive surface 212 ofbelt 210, the residual toner/developer and paper fiber particlesadhering to photoconductive surface 212 are removed therefrom atcleaning station E. Cleaning station E includes a rotatably mountedfibrous brush in contact with photoconductive surface 212 to disturb andremove paper fibers and a cleaning blade to remove the nontransferredtoner particles. The blade may be configured in either a wiper or doctorposition depending on the application. Subsequent to cleaning, adischarge lamp (not shown) floods photoconductive surface 212 with lightto dissipate any residual electrostatic charge remaining thereon priorto the charging thereof for the next successive imaging cycle.

Controller 229 regulates the various printer functions. The controller229 is preferably a programmable microprocessor, which controls all ofthe printer functions hereinbefore described. The controller 229provides a comparison count of the copy sheets, the number of documentsbeing recirculated, the number of copy sheets selected by the operator,time delays, jam corrections, etc. The control of all of the exemplarysystems heretofore described may be accomplished by conventional controlswitch inputs from the printing machine consoles selected by theoperator. Conventional sheet path sensors or switches may be utilized tokeep track of the position of the document and the copy sheets.

While the invention has been described in detail with reference tospecific and preferred embodiments, it will be appreciated that variousmodifications and variations will be apparent to the artisan. All suchmodifications and embodiments as may occur to one skilled in the art areintended to be within the scope of the appended claims.

We claim:
 1. A method for fabricating a semiconductor device comprising:(a) providing a semiconductor wafer having a main surface defining chipareas separated by V-grooves, the chip areas defining bonding pads andthree rows of photosites, wherein the photosites include innerphotosites, outer photosites and bonding pads; (b) depositing a clearlayer on the semiconductor wafer, (c) soft baking the semiconductorwafer; (d) exposing selective areas of the semiconductor wafer; (e)etching the clear layer covering the bonding pads and outer photositesfrom the semiconductor wafer; (f) hard baking the semiconductor wafer;and (g) depositing a first primary color filter layer over at leastfirst inner photosite and first outer photosite, the first primary colorfilter layer transmitting a primary color.
 2. The method for fabricatinga semiconductor device as in claim 1, further comprising dicing thesemiconductor wafer to provide semiconductor chips.
 3. A method forfabricating a semiconductor device comprising: (a) providing asemiconductor wafer having a main surface defining chip areas separatedby V-grooves, the chip areas defining bonding pads and three rows ofphotosites, wherein the photosites include inner photosites, outerphotosites and bonding pads; (b) depositing a first clear layer on thesemiconductor wafer; (c) soft baking the semiconductor wafer; (d)exposing selective areas of the semiconductor wafer; (e) etching thefirst clear layer covering the bonding pads from the semiconductorwafer; (f) hard baking the semiconductor wafer; (g) depositing a secondclear layer on the semiconductor wafer; (h) exposing selective areas ofthe semiconductor wafer; (i) etching the second clear layer covering thebonding pads and outer photosites from the semiconductor wafer; (j) hardbaking the semiconductor wafer; and (k) depositing a first primary colorfilter layer over at least first inner photosite and first outerphotosite, the first primary color filter layer transmitting a primarycolor.
 4. The method for fabricating a semiconductor device as in claim3, further comprising dicing the semiconductor wafer to providesemiconductor chips.